The present invention relates to closure and method for sealing a tube and, more particularly, to highly effective sealing closure and method which enable to establish vacuum conditions within a tube while the closure is positioned on the tube.
When handling potentially contaminated physiological fluids such as blood or urine of a patient, or any other hazardous material, it is necessary to provide highly effective removable and reinsertable sealing closure for the sampling tube. Such sealing closure should preferably feature an optimal combination of structure and material so as to achieve optimal sealing properties. Further, such sealing closure should preferably enable the establishment of vacuum conditions within the sample tube, so as to allow sampling of physiological fluids by using the vacuum collection method. Further, such sealing closure should preferably enable to maintain vacuum conditions within the tube for an extended period of time, until use.
Various attempts have been made to provide sealing closures for effectively sealing a sample tube so as to maintain vacuum conditions within the tube. An example is disclosed in U.S. Pat. No. 4,531,651. However, most of these closures feature an inner stopper portion made of elastomeric material, such as butyl rubber, constructed to be received at least partially within the tube; and an outer skirt portion made of non-elastomeric material, such as plastics material, disposed radially of the stopper portion. The inner stopper portion and the outer skirt portion are usually connected to each other by means of a mechanical connection. However, closures with such a mechanical connection between the stopper portion and the skirt portion are vulnerable to separation of the two portions and therefore to deformation of the closure.
Alternatively, the stopper portion and the skirt portion are sealed to each other by means of thermoplastic elastomers which are known to have limited compression set (memory) and low resistance to deformation. Thus, such sealing connection between the inner stopper portion and the outer skirt portion may decrease the air blocking properties of the overall closure.
An example of a closure having an inner stopper portion and an outer skirt portion made as an integral unit is disclosed in U.S. Pat. No. 5,385,253. The closure is made of an elastomeric material. However, the closure disclosed is specifically adapted for the establishment of sterile conditions within the tube, while the closure is in place, i.e., securely attached to the tube. The stopper portion of such closure features extensions defining passageways through which steam can penetrate into the tube during the sterilization process. However, such closure cannot be used for maintaining vacuum conditions within the tube since any substantial pressure difference may cause penetration of air into the tube through the passageways. Further, the inclusion of extensions on the stopper portion does not provide uniform distribution of pressures on the internal facet of the tube, which uniform distribution is necessary for maintaining vacuum conditions within the tube.
Thus, none of the disclosures mentioned above provides closure having an inner stopper portion and an outer skirt portion integrally made which is specifically adapted for establishing and maintaining vacuum conditions within the tube.
Further, none of the disclosures mentioned above provides method for the establishment of vacuum conditions within the tube while the closure is loosely positioned on the tube. Rather, a special instrumentation has to be used in order to keep the closure at a predetermined position with relation to the tube while establishing vacuum conditions within the tube.
There is thus a widely recognized need for, and it would be highly advantageous to have, a closure featuring good air blocking properties, high compression set and resistance to deformation, which enables to establish and maintain vacuum conditions within a tube.
It would be further advantageous to have closure and method which enable to establish vacuum conditions within a tube while the closure is loosely positioned on the tube, thereby eliminating the need to use special instrumentation for accurately holding the closure at a predetermined position with relation to the tube while establishing vacuum conditions.